Field of the Invention
The present invention relates to a motor controller, a motor control method, and a motor control program, all of which drive a motor by way of pulse width modulation.
Related Art
Conventionally, a rotation amount, speed or torque is controlled in a motor that drives machine tools, etc. A controller of the motor drives and controls the motor by determining a voltage instruction value based on various feedback values from the motor, modulating a voltage by way of a pulse width modulation (PWM) scheme, and applying the voltage to the winding of the motor.
Such a motor uses a maximum current during acceleration or deceleration, and is provided with a limiting current value so as to prevent overheating due to continuous use. Namely, the higher the motor temperature becomes, the lower the value of the current flowing through the motor will be restricted to.
Further, in the technical field of PWM control, it has been known that heat generation in a motor is also reduced by raising a pulse signal frequency (PWM frequency).
Meanwhile, when the PWM frequency is raised, the ON-OFF cycle of the switching elements in an inverter composing an amplifier will be shortened, which will in turn increase heat generation in the amplifier.
Therefore, a technique has been proposed, in which, when the motor temperature is low, the amplifier temperature is lowered by lowering the PWM frequency (for example, refer to Patent Document 1).    Patent Document 1: Japanese Unexamined Patent Application, Publication No. 2009-189181